Differences in dry weight partitioning and flowering phenology between native and non-native plants of purple loosestrife ( Lythrum salicaria L.)

Abstract

Invasive plants of Lythrum salicaria (purple loosestrife), a species native to Eurasia, exhibit different ecological strategies to indigenous plants by growing more vigorously. The hypothesis is tested that the more vigorous growth of invasive L. salicaria plants is a result of differences in dry weight partitioning between native and non-native plants. Plants of three native Central European and three non-native North American populations of L. salicaria were exposed to the same experimental conditions for 4 months. Size and growth related plant characteristics were measured in ten-day intervals in both native and non-native plants. From these characteristics, relative growth rate, reproductive effort and leaf weight ratio were calculated. The dependence of net photosynthesis on photon flux density in both native and non-native plants of L. salicaria was measured. Plants of the non-native populations grew taller than the native plants and produced, on average, twice as much dry weight of stems, leaves and primary lateral branches as plants of native populations but no significant differences in net photosynthesis time courses was found between the native and non-native plants. The native and non-native plants exhibited different dry weight partitioning patterns, connected with differences in flowering phenology. These differences probably affect competitive ability of the native and non-native plants and are also responsible for more vigorous growth of the non-native plants.